The present invention relates to a camera having a viewfinder, and more particularly to such a camera which is changed suitably for wide-angle photography, telephotography or macro photography by changing the focal length thereof.
Numerous compact cameras having lens shutters are already known. Some such compact cameras are provided with taking lenses of the type that the focal length can be changed between a relatively short focal length of about 35 mm suitable for wide-angle photography and a relatively long focal length of about 70 mm suitable for telephotography. Such focal length changeable cameras are provided with viewfinders of the type that the magnification of the finder is changeable according to the focal length of camera. Such a viewfinder has two concave lens for forming a finder optical lens system suitable for wide-angle photography. When the camera is changed suitably for telephotography, one of the two concave lenses is displaced from the optical path of the finder lens system simultaneously with the axial movement of the other concave lens, thereby changing the magnification of the finder suitably for telephotography.
Such a camera has a viewfinder which is place at some distance from the taking lens of the camera and has an optical axis parallel to the optical axis of the taking lens, and the result is a change in appearance and orientation of objects seen from different viewpoints, which is referred to as parallax. The error of parallax becomes greater as the camera is moved closer to the subject. For instance, when the camera is used at a distance of about 1 m, the viewfinder and the taking lens have substantially different views of the scene. This difference becomes greater when the camera is used for close-up photography. This leads to incorrect framing, or incorrect focusing.
For overcoming this parallax problem in the cameras that are used for close-up photography, it is known to use an optical wedge which is moved into and displaced from the optical path of the viewfinder to deflect the optical axis of the viewfinder optical system. However, in this case, the viewfinder optical system with its associated mechanism unavoidably becomes complicated. Specifically, the provision of such an optical wedge for deflecting the optical axis of the viewfinder requires the provision of complicated mechanism for inserting the optical wedge into the optical path of the viewfinder in order to cancel parallax error, in addition to the provision of mechanism for axially moving the objective lens of the viewfinder or optical system, or inserting one or more lenses into the optical path of the viewfinder in order to change the magnification of the viewfinder. Furthermore, a mechanism is needed to link these mechanisms with a mechanism for changing the focal length of taking lens.
An alternative and simpler way of overcoming the parallax problem is to provide two or more finder frames in the finder changeable according to the focal lengths of the taking lens or to place one or more marks in the finder indicating the center or the top of a finder frame.
Meanwhile, a recent tendency in such focal length changeable cameras is to provide zoom lenses as the taking lens. When a camera has a zoom lens, it must necessarily be equipped with a zoom finder which is changed in magnification corresponding to zooming of the zoom lens in order to provide the same views of the scene independently of the object distances. The zoom finder and the zoom lens, however, give different views of the scene because of the magnification of the zoom finder and the zoom lens. Therefore, although the above described means for overcoming the parallax problem are effective to correct parallax caused by object distances, they are unable to eliminate parallax error caused by the magnification of the zoom finder.